Regenerate old thumbnails after changing a theme

A theme change may require image sizes that were never generated for older uploads.

reGenerate Thumbnails Advanced can recreate the required image sizes.

Back up both files and the database before running the process.

Install and activate the plugin only from its official WordPress page.

Review the available thumbnail sizes and begin with one test image.

Regenerate that image, then inspect its post card on desktop and mobile.

If the crop looks wrong, also review the theme’s focal point or aspect ratio.

Do not remove old sizes without a backup and confidence that the previous theme no longer needs them.

For a large media library, run the job in stages during a quiet period.

Finally, open several old and new posts and check that no image is broken.

Plugin and demo links

A public live demo is not available; official plugin screenshots are linked below.

• Official download and installation
• Official screenshots

Official sources

• WordPress.org — reGenerate Thumbnails Advanced